$\dfrac{6}{4} + \dfrac{6}{3} = {?}$
$ = {\dfrac{6 \times 3}{4 \times 3}} + {\dfrac{6 \times 4}{3 \times 4}} $ $ = {\dfrac{18}{12}} + {\dfrac{24}{12}} $ $ = \dfrac{{18} + {24}}{12} $ $ = \dfrac{42}{12}$